Sunday, September 5, 2010

Impossible Coin Toss

There is an urban legend which has been around for many years to the effect that a professor teaching physics in a major university explained that it was feasible that, just by pure chance, the trajectory of the Brownian motion vibrating every water molecule in a cup might be "up," causing it all to evaporate in the twinkling of an eye.

"But," the professor is supposed to have said, "That's about as likely as this quarter landing on its edge and staying in that position when I throw it." And he supposedly threw the quarter across the amphitheatre - style classroom, and it landed on the floor on its edge and stayed there, upright.

Once many years ago, maybe around 1970, when I was alone in my parents' house in Philadelphia, I was thinking of the story, and on a lark threw a nickel across the room.

The nickel flew about 10 feet, landed on its edge on the linoleum floor -- and stayed there, upright.

I swear that that is a true story.


  1. When I was 5 years old, I was drinking Hawaiian punch. I spilled some on the linoleum floor and didn't tell anyone for fear of trouble.

    More data needed. Coin was thrown about 10 feet away. Ceiling was about 8 to 9 feet, so there wasn't too much upward arch covering this 10 feet. So, much of the energies are in the moving the coin away from you (perpendicular to gravity). so, lots of momentum. Did coin roll?
    How big of a runway did the coin have for this roll? (don't say it didn't roll or you'll have to explain that, that would be more interesting than staying on its edge). Are their hidden facts here, for sake of keeping the story interesting? (i.e. did the nickel roll in near parallel fashion, to a wall and lean on the wall and stay upright that way . . . or some other hidden factor . . .(separated tiles and nickel rolled into seam???)) Are you, without saying so, claiming 'other' influences?

  2. Hi, Tom.

    When you started talking about Hawaiian P{unch, I thought that you were going to say that Brownian Motion mkade it all dry up in an instant.

    This Hawaiian Punch business is serious. I'm going to tell Dad.

    I was sitting at the kitchen table, my back to the back door. The coin reached an apogee of about 5 feet, and it landed on the floor in front of the dining room -- and froze. No bouncing, no rolling. And, of course, as I said, it was standing on its edge. It was a one-in-a-trillion incident.

    Re "other" influences, the house was haunted, so I always wondered if I was being toyed-with.

  3. I stepped in that Hawaiin Punch, 3 yrs later. It wasn't pleasant. I'm telling Dad ;-)

  4. Re "one-in-a-trillion incident," ultimately-skeptical skeptics online pooh-pooh all coincidences by saying, "ALL incidents are one-in-a-trillion."

  5. In other words, "Is there anything remarkable about a man who CAN'T do anything but win games of chance?" An ultimately-skeptical skeptic says, "No! Not at all! Each prospective series is EQUALLY unlikely. If fate happens to choose the one where the man keeps winning, that's okay and completely non-remarkable."

    Why is that analysis wrong?